Neoplastic cells are essentially parasitic forms of life and as such depend upon the host for the maintenance of a favorable environment for growth and development. The rate of growth of these neoplastic cells is frequently greater than that of their host tissues and the regulation of this growth process may not be the same as that of the host. Therefore, a control of entry of substances into these neoplastic cells may be the controlling factor in their abnormal rate of growth. This proposed research program hopes to demonstrate whether transport properties of neoplastic cells have specific metabolic advantages over normal cells and whether these differences may be useful in diagnosis or inhibition of neoplastic growth. We propose to: (a) define the functional properties of the membranes of both normal and neoplastic cells; (b) to determine the degree of sodium dependent and sodium independent amino acid transport in erythroid, myeloid, and lymphoid cells of both normal and neoplastic cells; (c) to develop tissue culture systems which will force neoplastic cells to develop into normal cells; (d) to investigate the turnover of membrane proteins as the cells become neoplastic; and (e) to identify those properties of neoplastic cells which have an advantage in growth properties over normal cells. Studies on the transport properties of both normal and neoplastic cells should lead to a better understanding of the controlling factors in neoplastic cellular growth.